Double-acting swashplate compressor

ABSTRACT

In preferred form, a fluid compressor for an automobile air conditioning system having three cylinders within a cylinder block which is supported within a compressor casing by one end of the casing. Pistons are reciprocated within the cylinders by piston rods which extend through a cylinder head into the interior of the casing. A drive shaft extending through the other end of the casing rotates an inclined swashplate which coacts with the piston rods to reciprocate the pistons. A high pressure discharge passage is centrally formed on both ends of the cylinder block and are interconnected by a passage axially extending therebetween. A low pressure intake passage is formed on the cylinder ends and encircles the discharge passage.

Unlted States Patent 1 1 1 1 3,746,475 Johnson July 17, 1973DOUBLE-ACTING SWASHPLATE Primary Examiner-William L. Freeh COMPRESSORAttorney-W. S. Pettigrew. .I. C. Evans and K. H. [75] Inventor: Ralph S.Johnson, Rochester, Mich. M [73] Assignee: General Motors Corporation,Detroit, MlCh. [22] Filed: Feb. 3, 1971 In preferred form, a fluidcompressor for an automobile 1 PP No.1 112,335 air conditioning systemhaving three cylinders within a cylinder block which is supported withina compressor 52 us. (:1. 417/269 easing by one end of the easing Pistonsare 511 1m. (:1. F04b 1/12 Preeeted Within the cylinders by P reds which581 Field of Search 417/269; 91/502 tend through a cylinder head intothe interior of the casing. A drive shaft extending through the otherend [56] References Cited of the casing rotates an inclined swashplatewhich co- UNITED STATES PATENTS acts with the piston rods to reciprocatethe pistons. A- I high pressure discharge passage is centrally formed on2,991,723 7/1961 Zabaty 1 417/269 both ends f the i d l k d areinterconnected 3,552,886 l/197l Olson 417/269 b n t d th b t A I w 2479876 8/1949 Sherman 417 269 y a pasiage y m e 0 2945444 7/1960 Leissner n417/269 pressure lntake passage is formed on the cylinder ends 3,215,34111/1965 Francis 417/269 and encircles the dischaige P 3,538,706 11/1970Tocpel 417/269 FOREIGN PATENTS OR APPLICATIONS Germany 91/502 I 1 Claim,7 Drawing Figures DOUBLE-ACTING SWASHPLATE COMPRESSOR This inventionrelates to fluid compressors for air conditioning applications.

It is desirable that fluid compressors in automobile air conditioningsystems be lightweight and subject to modification to change thecompressor capacity. Another desirable feature is that the temperatureof the compressor be kept as low as possible.

The subject air conditioning compressor utilizes a cylinder block havingthree cylinder bores arranged symmetrically about a centerline of theblock. Pistons within the cylinders are connected to piston rods whichcoact with a swashplate drive assembly to reciprocate the pistonscausing compression of fluid. The capacity of the compressor is easilychanged by simply providing a cylinder block with smaller diameter boresand matching small diameter pistons. Because of the symmetricalarrangement of the bores and pistons, no unbalancing is encountered dueto this change. An annular channel in the cylindrical surface of thepistons is varied in depth to provide the same weight for both sizepistons. This permits use of the same swashplate drive assembly in allcapacity compressors.

The subject compressor includes cylinder heads covering either end ofthe cylinder block to define the compression chambers on either side ofthe doubleended pistons. A centrally located discharge passageway isformed within the end cylinders for receiving fluid from the compressionchambers after compression. A bypass passageway axially through thecylinder block and between the cylinder heads interconnects the twodischarge passageways with an outlet from the compressor. Intakepassageways formed in the cylinder heads encircle the dischargepassageways and are separated therefrom by more or less circular wall orridge portions. The inlet passageways open directly to the interior ofthe compressor casing. By this arrangement, the warm discharge fluid ofthe compressor is surrounded by the relatively cool fluid in theinterior of the casing. This keeps the temperature of the compressor ata desirably lower temperature.

Therefore, an object of the invention is the provision of a lightweightfluid compressor whose capacity may be readily varied simply by thesubstitution of a cylinder block assembly having different diametercylinder bores with pistons to match.

A further object of the invention is to provide a lightweight fluidcompressor in which the high-temperature discharge fluid is confined tothe central region of the cylinder block and where it is surrounded bythe lowtemperature intake fluid.

Further objects and advantages of the present invention will be apparentfrom the following detailed description, reference being had to theaccompanying drawings in which a preferred embodiment is clearly shown.

IN THE DRAWINGS:

FIG. 1 is a vertical sectioned view of the compressor;

FIG. 2 is a sectioned view along section line 2--2 in FIG. 1 and lookingin the direction of the arrows;

FIG. 3 is a sectioned view along section line 3-3 in FIG. 1 and lookingin the direction of the arrows;

FIG. 4 is a sectioned view along section line 44 in FIG. 1 and lookingin the direction of the arrows;

FIG. 5 is a sectioned view along section line 5-5 in FIG. 1 and lookingin the direction of the arrows;

FIG. 6 is a sectional view taken along section line 6-6 in FIG. 5 andlooking in the direction of the arrows; and

FIG. 7 is a partial view of a smaller capacity compres sor similar toFIG. 1 and broken away to reveal a smaller diameter cylinder and piston.

In FIG. 1, a compressor 10 is illustrated. Compressor 10 includes acylindrical casing or housing 12 having and members 14 and 16 enclosingan interior space 18. The end member 14 is sealed in relation to housing12 by an O-ring 22. In turn, the flange 20 is joined to the housing 12by a weld 24 to produce a leakproof connection. The other end member 16is fastened to the housing 12 by a crimp 26. An Q-ring type sea] 28between the end 16 and casing 12 produces a leakproof connection.

A compressor cylinder block assembly 30 is supported within the interiorspace 18 by the end 16. The cylinder block assembly 30 includes acylinder block 32 with three parallel cylinder bores 34 arrangedsymmetrically about the axis of the cylinder block. The ends of thecylinder block 32 are covered by valve plates 36 and cylinder heads 38and 39. On one end, the valve 36 and cylinder head 39 are securedbetween the end member 16 and the cylinder block 32 by three boltfasteners 42 which are threaded into the end 16. An end cover 40 extendsover the cylinder head 38 which is on an opposite end of the block toend member 16.

Three pistons 44 are disposed withinthe cylinders 34 for reciprocation.The pistons 44 have a channel 46 formed in their cylindrical surface andannular leg portions 48 which contact the cylinders 34. Three pistonrods 50 are connected at reduced diameter ends 52 to pistons 44. Thepiston rods 50 extend from piston 44 through a valve plate 36, thecylinder head 38 and cover 40 into the interior l8. O-ring type seals 54encircle the piston rods 50 and prevent fluid leakage from cylinders 34therebetween.

A swashplate 56 is affixed to a drive shaft 58 for rotation and includesparallel face surfaces which are at an inclined angle with respect tothe drive shaft axis. An end 59 of the shaft 58 is supported in abearing recess 60 formed within a boss 61 of cover 40. Needle bearings62 between end 59 and boss 61 are provided to reduce frictiontherebetween during rotation. The shaft 58 extends through the interior18, through a bore 64 in end 14 and through a cylindrical] extension 66on the end 14. Needle bearings 68 between shaft 58 and bore 64 reducefriction therebetween, during rotation. A seal assembly 70 supported bycylindrical extension 66 encircles the shaft 58 and prevents the loss offluid from interior space 18. The exterior end 72 of shaft 58 is adaptedto be rotated by the auto engine to cause rotation of the shaft 58 andswashplate 56.

The swashplate 56 is pressed onto shaft 58 for rotation therewith. Thecircular swashplate 56 is inclined with respect to the axis of shaft 58so that upon rotation of the shaft, the peripheral edge of theswashplate moves axially with respect to the shaft 58. U-shaped saddlemembers 74 which are formed in the ends of piston rods 50 straddle theperipheral edge of the swashplate 56. Semi-spherical thrust bearingshoes 76 between the face surfaces of the swashplate 56 and per tions 77of the saddle members 74 slide along the face surfaces of swashplate 56as it is :rotated. The pistons 44 and piston rods 50 are reciprocated bythe peripheral edge as it moves axially with respect to shaft 58 duringrotation. This translation of rotational movement of shaft 58 intoreciprocal movement of the piston rods 50 and pistons 44 produces thefluid pumping action. As the swashplate 56 rotates and moves the pistonrods 50 and pistons 44 axial thrust forces are exerted on shaft 58.Needle bearings 78 between the swashplate 56, end plate 40 and end 14reduce friction caused by the axial thrust force.

When the pistons 44 are moved within the cylinders 34, fluid iscompressed on one side of the piston while fluid is drawn into thecylinder on the other side of the piston for subsequent compression. Thefluid is drawn into the left-hand compression chamber in FIG. 1

through an intake passage or channel 80 formed in the end 16 by anannular recess. The fluid passes from interior 18 through the passage 80and into intake ports 82 in cylinder head 38, as best shown in FIG. 5.

Fluid is drawn into the right-hand cylinder 34 through intake ports 84in cover 40 and cylinder head 38, as best shown in FIG. 4. Fluid passesinto cylinder 34 under the control of reed valves 86 formed in the valveplate 36, as best shown in FIG. 3. The reed valves 86 are thin, flexibleportions of plate 36 separated from the remaining portion of the plateby a cutout 88. Elongated holes 90 in the valve plates 36 permit pistonrods 50 to pass through the valve plate 36. The valve plate covering theleft end of the cylinder block 32 is identical to plate 36 in FIG. 3with holes 90 therein. The reed valves 86 prevent hydraulic fluid withinthe cylinders 34 from being discharged through the intake ports 82 and84 as fluid is compressed.

Fluid is discharged from the cylinders 34 through outlet ports 92 in thecylinder heads 38 as shown in FIGS. 4 and 5. The fluid passes fromoutlet ports 92 into discharge passages 94 formed by a centrally locatedrecess in the end member 16 and the cover 40. The discharge passages 94are positioned centrally on the end 16 and the cover 40 and a more orless circular wall 96 on the end member 16 separate the dischargepassage 94 from the intake passage 80. An axially directed crossoverpassage 98 axially through the cylinder block 32 interconnects thedischarge passages 94. An outlet opening 99 directs the fluid from thecompressor 10 through an outlet fitting (not shown) therein which alsoacts as a pressure relief valve.

Fluid is prevented from being drawn from the discharge passages 94 backinto the cylinders 34 by reed valves 100 which cover the outlet ports92, as shown in FIG. 6. The reed valves 100 are held against thecylinder head 39 by a rivet fastener 102 and a backup strip 104. Thebackup strip 104 has a tab 106 which engages a hole 108 for aligning thereed valve 100 over the outlet port 92. The overlying backup strip 104restricts the movement of the reed valve 100 to prevent excessivedeflection which might damage the reed valve.

An important feature of the compressor is its adaptability for changingcompressor capacity by substituting a new cylinder block having smallercylinders and smaller pistons. In FIG. 7, a compressor with smallercylinders and pistons is shown. A new cylinder block 110 with smallerdiameter cylinders 112 reduces the compressor capacity. Smaller diameterpistons 114 are used in the cylinders 112. The channel 116 of thesmaller diameter piston 114 is shallower than channel 46 in piston 44 inFIG. 1. This permits both pistons to be approximately the same weight.This is desirable for use of the same swashplate assembly in compressorsof varying capacity.

Also of importance in this compressor is the confinement of therelatively warm discharge fluid to a central region of the cylinderblock. In this region, it is encircled by cool fluid within the interiorof the casing. This reduces the compressors operating temperature aswell as the temperature of its outer surface.

While the embodiments of the invention herein described are preferredform, other embodiments may be tioning system comprising: a cylindricalcompressor casing with first and second end members enclosing aninterior space; a cylinder block assembly being supported by andfastened to said first end member within said interior space; saidcylinder block assembly including a cylinder block with cylinder boresextending therethrough normal to said first end member and arrangedsymmetrically about its axis, a valve plate on both ends of saidcylinder block covering said cylinder bores, a cylinder head on bothends of said cylinder block covering said valve plates; a cover on theend of said cylinder block opposite said first end member; pistons insaid cylinder bores forming compression chambers on either side of saidpistons; piston rods attached to said pistons and extending through oneof said cylinder heads and said end cover into said interior space; adrive shaft supported by said second end member and by said cover forrotation within said interior space; a swashplate affixed to said driveshaft between said cover and said second end member having parallel facesurfaces which are inclined with respect to the axis of said driveshaft; U-shaped saddle portions of said piston rods which straddle theperipheral edge of said swashplate and contact said face surfaces fortransforming rotational movement of said swashplate into linear re- Iciprocation of said piston rods and said pistons; an inlet openingthrough said first end member for passing low pressure fluid into saidinterior space; an annular intake passage formed in said first endmember; inlet means through said cylinder heads and said cover forpassing fluid from said interior space and said intake passage into saidcompression chambers; inlet valves formed in said valve plates forcontrolling fluid flow into said compression chambers; a dischargepassage in a central portion of said first end member separated fromsaid surrounding intake passage by an annular wall; another dischargepassage in a central portion of said cover in' terconnected to saidfirst discharge passage by a crossover passage through said cylinderblock and cylinder heads; outlet means through said cylinder heads forpassing fluid from said compression chambers into said dischargepassages; outlet valves formed in said valve plates for controllingfluid flow from said compression chambers; an outlet opening throughsaid first end member fluidly connected with said discharge passages forpassing fluid from said compressor.

1. A fluid compressor for an automobile air conditioning systemcomprising: a cylindrical compressor casing with first and second endmembers enclosing an interior space; a cylinder block assembly beingsupported by and fastened to said first end member within said interiorspace; said cylinder block assembly including a cylinder block withcylinder bores extending therethrough normal to said first end memberand arranged symmetrically about its axis, a valve plate on both ends ofsaid cylinder block covering said cylinder bores, a cylinder head onboth ends of said cylinder block covering said valve plates; a cover onthe end of said cylinder block opposite said first end member; pistonsin said cylinder bores forming compression chambers on either side ofsaid pistons; piston rods attached to said pistons and extending throughone of said cylinder heads and said end cover into said interior space;a drive shaft supported by said second end member and by said cover forrotation within said interior space; a swashplate affixed to said driveshaft between said cover and said second end member having parallel facesurfaces which are inclined with respect to the axis of said driveshaft; U-shaped saddle portions of said piston rods which straddle theperipheral edge of said swashplate and contact said face surfaces fortransforming rotational movement of said swashplate into linearreciprocation of said piston rods and said pistons; an inlet openingthrough said first end member for passing low pressure fluid into saidinterior space; an annular intake passage formed in said first endmember; inlet means through said cylinder heads and said cover forpassing fluid from said interior space and said intake passage into saidcompression chambers; inlet valves formed in said valve plates forcontrolling fluid flow into said compression chambers; a dischargepassage in a central portion of said first end member separated fromsaid surrounding intake passage by an annular wall; another dischargepassage in a central portion of said cover interconnected to said firstdischarge passage by a crossover passage through said cylinder block andcylinder heads; outlet means through said cylinder heads for passingfluid from said compression chambers into said discharge passages;outlet valves formed in said valve plates for controlling fluid flowfrom said compression chambers; an outlet opening through said first endmember fluidly connected with said discharge passages for passing fluidfrom said compressor.